Question

Solid urea, (NH2)2CO, burns to give CO2,N2, and liquid H2O. Its heat of combustion is -632.2 kJ/mol. Balance the equation for combustion of urea, and calculate the heat generated per mole of H2O formed. (Enter in kJ.)

Answer 1

2(NH2)2CO +3O2 ==> 2CO2 + 2N2 + 4H2O dH = -632.2 kJ/mol*2 mol = 1264.4 kJ/2 mol urea or 4 mols H2O.
dH for 1 mol H2O is 1264.4/4 kJ.

Answer 2

you divide the given by 2, not multiply, since there are double the moles of H2O compared to urea in the balanced equation. make sure you note that it’s still negative